Coupler system in electric musical instruments



R. P. MORK COUPLER SYSTEM IN ELECTRIC MUSICAL INSTRUMENTS Filed Nov. l8, 1948 2 Sheets-Sheet l RAYMOND F! MORK INVENTOR- Qflw 1 Wk.

A TTOHNEYS R. P. MORK June 19, 1951 COUPLER SYSTEM IN ELECTRIC MUSICAL INSTRUMENTS Filed Nov. 18, 1948 2 Sheets-Sheet 2 RAYMONDI? Monk 8 8. SEE 2- 2536 33 28 .E w E m x mm T. .t K E E V M Ma INVENTOR. BY QZZMQ ATTORNEYS 8 60 wZOh 4 omm O...

kw mm Patented June 19, 1951 COUPLER SYSTEM IN ELECTRIC MUSICAL INSTRUMENTS Raymond P. Mork, Cincinnati, Ohio, assignor to The Baldwin Company, Cincinnati, Ohio, a corporation of Ohio Application November 18, 1948, Serial No. 60,808

13 Claims. (Cl. 84-117) My invention relates to keyboard electrical musical instruments of an organ type wherein complex electric oscillations corresponding to musical tones may be modified as to harmonic content by various tone color circuits to produce headers and the tone color circuits normally associated therewith as 4 (four foot), 8', 16' etc., .in accordance with pipe organ terminology, to indicate the pitch relationship between the musical tones corresponding to the oscillations collooted by such headers and modified bysuch tone color circuits. Those skilled in the art know that on the manual keyboards 8' refers to normal pitch, 4' refers to an octave above normal, 16' to an octave below, etc.

In particular, my invention relates to the problem of providing circuits for coupling headers of one designation, such as 8', associated with one keyboard. to tone color circuits of other designations, such as 16', normally associated with the same keyboard, or' for coupling headers of one designation in one keyboard to either similarly or dilferently designated tone color circuits associated normally with other keyboards.

The function of various coupling circuits, or couplers, is to connect various headers to various tone color circuits, such as above, so that tones produced by the playing of respective keys of one keyboard may have either the characteristics determined by the tone color circuits normally associated with that keyboard but at octavely related pitches or the characteristics determined by the tone color circuits normally associated with another keyboard at either the same pitch or at octavely related pitches.

The name of a particular coupler is usually composed of twoparts. The first part, :for instance Swellto Great, indicates which tone color system is connected to which keyboard. The second part, for instance 16', indicates the pitch relationship between the normal pitch of respective tone color circuits and the pitch which will be produced with the coupler in use.

In the above patent to Kock there are no teachings with respect to coupling one header to another so that oscillations normally collected by one header follow the path of the oscillations normally collected by others.

Simple circuits have, however, been employed by prior workers in the art for the purpose of coupling electrically one keyboard to another so that tones produced by playing the keys on one keyboard may have the characteristics of tones normally associated with another keyboard, For instance, Vierling in his Patent No. 1,933,299 disclosed keyboard coupling of the type wherein notes played on one keyboard may be modified by tone color circuits for that keyboard and/or by tone color systems normally employed for other keyboards. Further, in a copending application, Serial No. 756,126 of John F. Jordan, filed June 21, 1947, entitled An Electric Organ, are disclosed circuits by means of which tone currents transmitted by headers of the Great manual may be switched through certain tone vcolor circuits normally effecting the tone currents derived through the Swell manual. The above mentioned art does not, however, appear to be applicable, as will be explained below, to more elaborate or versatile instruments wherein numerous octave and/or keyboard couplers are desired.

Therefore, it is a primary object of my invention to provide a complete and practical system of couplers for use in electric musical instruments.

It is another object of my invention to provide a circuit by means of which oscillations collected by one header associated with a keyboard in an electric musical instrument may be transmitted to tone color circuits normall associated with another header of the same keyboard.

It is also an object of my invention to provide a plurality of circuits for a particular coupler by means of which oscillations collected respectively by a plurality of headers associated with a keyboard may be transmitted respectively to tone color circuits normally associated with other headers of the same keyboard.

It is a further object to provide coupler circuits by means ofwhich oscillations collected by one or more headers, designatable as 2, 4', 8, etc.,'associated with one keyboard in a multikeyboard electric musical instrument may be transmitted respectively to tone color circuits associated with one or more similarly designatable headers of other keyboards in said instrument.

An additional object is to provide coupler circuits by means of which oscillations collected by one or more headersassociated with one keyboard in a multi-keyboard instrument may be transmitted respectively to tone color circuits 'ators B1 and C1, respectively (not shown).

accuse normally associated with one or more headers of other keyboards in said instrument, which tone color circuits normally modify oscillations which are octavely related to those oscillations which may be transmitted thereto by said coupler circuits.

It is a further object of my invention to provide coupler circuits as in the preceding objects such that a negligible quantity of oscillations will be transmitted therethrough from one header to another header. 7

It is a still further object to provide such 'coupler circuits as provided in the preceding objects which will perform their required functionswith a minimum of attenuationof the oscillations transmitted through said coupler circuits.

Another object is to provide coupler circuits as in the preceding objects, the closure of. which circuits will not causean appreciable attenuation of oscillations carried by related circuits.

Still another object is to provide such'circuits as in the preceding object which, when open, will not allow the leakage of appreciable quantities of oscillations therethrough.

A still further object of-my invention is to provide circuits as in the preceding objects which are basically simple, requiring a minimum of circuit components, such as resistors and connecting leads, so that the circuits will be economical and will require a minimum of assembly time. 7

These and other objects which will be apparent to one skilled in the art upon reading these specifications, I accomplish by those circuits and arrangements of parts of which I shall now set forth exemplary embodiments. Reference is made to the drawings forming a part hereof and plete coupler system according to my'invention.

The teachings of Kock in Patent N0. 2,233,948

are employed in conjunction with my invention insofar as the keying and collecting of oscillations are concerned. Specifically, in Figure 1 generator B2 and C of a series 'of generators producing complex electric oscillations corresponding to musical tones are connected, as 65' shown, through decoupling resistors I and 2 respectively, to double-pole playing key actuated switches 3 and 4, respectively, which simu1taneously switch through separate pairs of contacts complex oscillations from octave higher gener- An 8' header 5 collects the normally pitched oscillations as shown, while octave higher oscillations are collected by a 4 header 6. Similarly,

the amplitude of lower frequency oscillations with respect to higher frequency oscillations, the purpose being to compensate for the preferential attenuation of the higher oscillations by filter type tone color circuits, known in the art, which I employ in conjuction with my invention.

Jordan, in the above mentioned application,

; shows in his drawing a system of coupling which I have illustrated in Figure 3 of my drawings. Referring to Figure 3, leads I! and I2 from 4 and 8' headers respectively of a Swell manual transmit oscillations from generators connected through key switches in the Swell manual in a manner similar to that of Kock, as described in Figure l. The 4' and 8' header leads l3 and and M respectively serve a similar purpose for a Great manual. Tone color circuits, indicated generally as TC, are connected to respective header leads through decoupling resistors l5, 15a, [51), etc. Jordan provided a Swell to Great 8 coupler by connecting a switch l6 designated also as S-"G 8 (Swell to Great'8), between the Great header leads l3 and I4 and Swell tone color circuits [8, 18a, lBb andlac through se arate decoupling resistors ll, Ila, ill) and Ho respectively. It can readily be seen that oscillationscarried by the Great header leads l3 and M will be modified upon the closure of the switch IE and tone color switches 19, I911, I91) and ['90 by the respective tone color circuits I8, l8a etc.,

of the Swell manual. However, only negligible quantities of oscillations carried by the Swell header leads H and I2 can pass to the Great header leads l3 and ll and thence through the Great tone color circuits id and 'ISe, because they sufiier considerable "attenuation in passing, for instance, from lead ll, through resistor l-5 to tone color circuit [8, and still more attenuation is passing from there-through the high resistance H to the low impedance Great header lead l'3.

Although Jordans circuit ispractical in an instrument having one or two couplers, it cannot be used satisfactorily in an instrument having many couplers. In the first place, for every header which is coupled to tone color circuits'of another keyboard, there are required as many additional decoupling resistors as there are tone color circuits. Secondly, the connecting of a multiplicity of couplers to the same tone color circuits results in a multiplicity of parallel paths between coupled headers, resulting not only in serious attenuation of oscillation strengths, but in other effects which will be understood more easily after a description of my invention;

Vierlings coupling circuits, as disclosed in the above patent, are not applicable to an instrument of the type described herein, because the direct coupling of one header with another reduces to one-half the impedance to ground of each header, resulting in excessive attenuation of oscillations. Also the Vierling couplers are not unidirectional in the above sense and therefore do not conform to common practice in orkey switches 1 and 8 provide for the keying recans. Y I

spectively of oscillations from generators B3 and C3 (an octave lower than 282 and C2, respectively) to the header 5 and from 3B2 and C2 to the header 6. I may also similarly employ additional Great I It will be apparent then, that in the development of a more complete and Versatile instrument employing numerous coupler circuits, I faced the problem of providing coupler circuits which headers and key switches for additional 00- D the'desired'functions Without the tavely related oscillations such as 2' and 16. In a manner also similar to that taught by Kock in the above patent, I employ a plurality of attenuating resistors 9 and lfl for the purpose of disadvantages described above. I In order to describe my invention as it appl-ie to different types-of couplers, I show in Figure 1 leads 20 and 21 from 8" and I6 Swell manual producing at the output end of headers 5 "and 6 76 headers respectively (not shown), and leads 22 and 23 from- 8' and 16' Pedal headers respectively (not shown), all of which headers may collect oscillations from their respective keyboards in a manner similar to that of Great headers and 6, to which are connected leads 25 and 24 respectively.

According to my invention I employ decoupling resistors 26-29, inclusive, in series with leads 24, 25, 20 and 2|, respectively: To the output ends of decoupling resistors 25-23 may be connected respectively suitable electronicamplifiers 30-33 respectively, shown as blocks labeled ,A! It is not essential that I employ amplifiers in conjunction with my invention, but certain advantages which I shall describe below, are derived from their use.

The outputs of the respective amplifier circuits -3033 may be modified selectivelyin a manner known in the art by tone color circuits 34 and 35, 36 and 31, 38 and 39, 40 and 4|, respectively. The selection of tone color circuits 34- is made by closure of respective-tone color switches .42, 42a, etc., connected in series therewith. If I do not care to couple the Pedal tone color circuits to other headers, I may connect such tone color circuits through individual decoupling resistors, as shown in Figure 1, to respective header leads 22 and 23 without amplification. I must provide, however, a stage of amplification 43 for Pedal output, it I have employed a stage for the outputs of each respective Swell and Great header, for the purpose of maintaining the correct phase relationship between the Pedal output and the other outputs. I may provide individual expression controls 44-46, a final amplification circuit 41 and an electro-acoustic system 48 connected as shown in Figure 1.

According to my invention, I provide a circuit between a point in one header lead on the input side of its decoupling resistor to another header lead-on the output side of its decoupling resistor.

For example, in Figure 1, a Swell to Swell 4' coupler comprises a connection from one terminal of a switch 49 to the lead 20 at a point 50 adjacent to the input end of the decoupling resistor 28, a decoupling resistor 5| connected between the other terminal ofthe switch 49, and the header lead 2| at a point 52 adjacent to the output end of the decoupling resistor 29, and a bypass or grounding resistor 53 connecting the junction of the resistor 5| and switch 49 with a. common return-path, which I shall hereafter refer to as ground. Closure of the switch 49 provides a path for 8' oscillations from the Swell manual to the Swell tone color circuits 40 and 4| normally modifying 16 oscillations, the result being SuperOctave coupling. I mayat the same time similarly connect oscillations from a 4 header lead (not shown) to the output end of resistor 28 in the 8' header lead 20, thereby passing 4 oscillations through v8' tone color circuits. Such a coupler circuit isshown indetail in Figure 4, and will be described hereinafter.

Also, I provide a Swell to Great 4' coupler by employing a double-pole switch 54 in a similar manner to connect the Great header leads 24 and 25 with Sewell header leads 20 and 2| respectively, the connections being respectively at the input ends of decoupling resistors 25 and 21 and at the output ends of decoupling resistors 28 and 29. Thus, 4' and 8' oscillations from the Great manual are' caused to pass through tone color circuits normally affecting the 8' and 16' oscillations respectively of the Swell manual. Since, as mentioned above, I may prefer the 8' and 16' Pedal header leads with the 8' and 16 Swell header leads respectively, as shown.

Having thus provided representative types of couplers for electric musical instruments I shall now present an analysis of the conditions which exist at a point such as 52 of Figure 1, wherein three coupler paths converge with the header lead 2 I. Such an analysis may be aided by a circuit such as that of Figure 2 wherein conditions at the point 52 of Figure 1 are simulated. A corresponding point 52in Figure 2 isshown connected to the control grid of a thermionic tube 33a, having the usual anode and cathode circuits in connection therewith to provide an amplification circuit corresponding to 33 of Figure 1. Branch circuits 25a, 20a and 23a from the point 52 of Figure 2correspond to respective coupler circuits and to header leads 25, 20 and 23 of Figure 1. Branch Zla. from the point 52 of Figure 2 corresponds to the header lead 2| of Figure 1. The switches 54a, 49a and 55a correspond respectively to the pertinent poles of the double-pole switches 54, 49 and 55. The decoupling resistors such as 5| in Figure 1, in each branch circuit, being of the same order of magnitude, have been labeled R1 for the purpose of this analysis. The grounding resistors, such as 53 of Figure l, in each branch circuit are, for a similar reason, labeled R2. The resistors R3 in each branch represent the impedance to ground of each header. The arrow labeled n indicates that my analysis will apply to a general case where couplers in addition to those shown in Figure 1 may be employed. n is the total number of coupler circuits which are connected to the point 52. Assuming an oscillation signal 21 applied to the signal lead 2|a. (this would correspond to an oscillation keyed into the 16' header lead of the Swell manual), I shall consider first the condition wherein all n switches are open; If I make R1 much greater than R3, the signal level e 2 at point 52 then may be given by the following general expression, the input impedance of the tube being considered as infinite in this analysis:

e (all switches open) e which reduces to:

0 (all switches closed) Since R1 is much greater than R3, the expression reduces very nearly to:

e2(n switches closed) Assuming definite ratios between values of R1 and R2 I have found that if R2 is of the order of of R1, there will not be an appreciable reduction in the signal level a between the condition where no" switches are closed and' that when any .or all switches are closed. Specifically, if the value of n is 6 (a condition such as may easily exist in theS' Swell header of Figure 4, which will be described hereinafter) r 2 (for open switches) c and c (for all closed switches) e This means that, although the maximum signal level (which loss can be compensated for by amplification), the ratio of .62 from the open-switch condition to the closed-switch condition, is only /14 A typical set of values for the above resistors is:

7 Ohms R1 33,000 R2 i i e 10,000 Rs i 900 It is'obvious that the selection of a ratio between R1 and R2 involves some compromises. First, it is desirable to make R2 as small as possible to reduce the change in e2 caused by closing coupler circuits, but the lower R2 is made the greater becomes the load on the headers being coupled as coupler switches are closed, and the greater the drop in e1. Secondly, it is desirable to make decoupling resistors R1 as high as possible for maximum decoupling, or anti-robbing,

as known in the art, but on the other hand, the higher R1 is made, the more the hum voltage that is picked up by capacitance coupling to the heater circuits of the thermionic tubes, such as 33a, used for amplification. (This applies to a practical system employing alternating current for the heaters of such tubes.) I may, as mentioned above, omit amplification circuits, but this requires much higher outputs for oscillation generators in order to provide a sufiicient signal level input to the tone color circuits.

The grounding resistors, such as 53, in Figure 1 serve a dual function. As described above, they reduce the change in signal level on a given header from coupler open to coupler closed condition. Also, they reduce the amount of capacitance leakage through open coupler switches to other circuits. For example, if a signal is present on the header lead 20 of Figure 1 and the switch 59 is open, the grounding resistor 53 provides a relatively low impedance to ground as compared with that through the resistor 51 to the header lead 2! or to the amplifier 33. This is important in instruments having sub-octave couplers, because spurious sub-octave oscillations are much more noticeable than similarly or higher pitched octavely-related oscillations. This is another reason why the Jordan circuit, as mentioned'above, is unsatisfactory for meeting certain objects of my invention.

In Figure 4 I show a more complete system of couplers by employing the basicnovel circuits illustrated in Figure 1 and by adding an additional header leadfor each keyboard, as shown. I'provide switches 60-85 connected as shown,

for thefollowing couplers} I Figure 2,- are created along the auxiliary lead or header 18, from the-8' Swell header lead it to other header leads. a i

I do not "wish to be limited in my invention to the specific circuits disclosed herein. It can readily be seem-for instance, that the circuits of Figure 4 may be further expanded to include additional headers,- such as 2", carrying oscillations an octave higher than those present in the 4' headers. Also, in a manner similar to that shown, I may employ Great tone color circuits for modifying Swell oscillations. It is also within the scope of my invention to provide additional similar'coupler circuits within keyboards for octave coupling or to provide additional similar circuits so that oscillations keyed by any keyboard may be modified by tone color circuits in any or all of the remaining keyboards, which circuits normally modify oscillations either at the same ireqi gncy or at octavely related frequencies.

Other modifications may be made in my invention without departing from'the spirit of it. Having thus described my invention by the use of exemplary circuits, what I claim as new and desire to secure by Letters Patent is:

1. In an electric musical instrument having a plurality of keyboards, a plurality of headers for each keyboard for collecting respectively octavely'related oscillations designatable as 4.- foot, 8 foot, 16 foot etc., separate tone color circuits for each keyboard associated with leads from such headers similarly designatable, and couplers acting selectively to couple headers of one keyboard with the leads of the same designation of tone color circuits of another keyboard, and with leads of said tone color circuits of divergent designations.

2. Inan electric musical instrument having at least one keyboard, a plurality of headers for said keyboard for collecting respectively oc-' tavely related oscillations designatable as 4 foot, 8 foot, 16 foot etc., separate tone color circuits associated with such headers and similarly designatable, a decoupling impedance located in series in each such header, and coupler circuits, each connecting the input end cfan impedance in series in a; header of one designation with the output end of an impedance in series in a header of divergent designation.

3; The combination claimed in claim 2, wherein said coupler circuits comprise each a switch and a first impedance in series,said switch being adjacent said input end'a'nd said first impedance being adjacentsaid' output end, and a second impedance connected between the junction of said switch with said first impedance and a common return path for said oscillations.

4. In an electric musical instrument having a plurality of keyboards, a plurality of headers for each keyboard for collecting respectively octavely related oscillations designatable as 4 foot, 8 foot, 16 foot etc., separate tone color circuits for said keyboards associated with such headers and similarly designatable, a decoupling impedance located in series in each such header and a plurality of coupler circuits each connecting the input end of an impedance in series in a header of one keyboard with the output end of an impedance in series in a header of divergent designation of another keyboard.

5. The combination claimed in claim 4, wherein said coupler cercuits comprise each a switch and a first impedance in series, said switch being adjacent said input end and said first impedance being adjacent said output end, and a second impedance connected between the junction of said switch with said first impedance and a common return path.

6. In an electric musical instrument having a plurality of keyboards, a plurality of headers for each keyboard for collecting respectively octavely related oscillations designatable as 4 foot, 8 foot, 16 foot etc., separate tone coler circuits for said keyboards associated respectively with such headers and similarly designatable, a decoupling impedance located in series in each such header, and coupler circuits, each connecting the input end of an impedance in series in a header of one designation in one keyboard with the output end of an impedance in series in a header of the same designation of another keyboard.

7. The combination claimed in claim 6 wherein said coupler circuits comprise each a switch and a first impedance in series, said switch being adjacent said input end and said first impedance being adjacent said output end, and a second impedance connected between the junction of said switch with said first impedance and a common return path.

8. In an electric musical instrument having at least one keyboard, the combination of a plurality of headers for such keyboard for collecting respectively octavely related oscillations, separate tone color circuits for said keyboard associated with said headers, a plurality of decoupling impedances respectively connected in series with said headers, thermionic tubes each having an anode, a control grid and a cathode, the output end of said impedances being respectively connected to the grids of said tubes, the cathodes of said tubes being connected to a common return path, the plates of said tubes being respectively connected to at least one of said tone color circuits, a coupling circuit between the input end of one of said decoupling impedances and the output end of another of said impedances, said circuit comprising a switch connected to said input end, a first impedance in series with said switch and connected to said output end, and a second impedance connected from the junction of said switch with said first impedance to said common return path.

9. In an electric musical instrument having a plurality of keyboards, the combination of a plurality of headers for each keyboard for collecting respectively octavely related oscillations designatable as 4 foot, 8 foot, 16 foot etc.. separate tone color circuits for each keyboard associated with said headers, a plurality of decoupling impedances respectively connected in series with said headers, a plurality of thermionic tubes each having an anode, a control grid and a cathode, the output end of said impedances being respectively connected to grids of said tubes, the cathodes of said tubes being connected to a common return path, the plates of said tubes being respectively connected to at least one of said tone color circuits, and coupling circuits respectively connected between input ends of decoupling impedances in series with the headers of one keyboard and output ends of decoupling impedances in series with headers of similar designations of another keyboard.

10. The combination claimed in claim 9, wherein each coupling circuit comprises a switch and a first impedance in series, said switch being adjacent said input end and said first impedance being adjacent said output end, and a second impedance connected between the junction of said switch with said first impedance and a common return path.

11. In an electric musical instrument having a plurality of keyboards, the combination of a plurality of headers for each keyboard for collecting respectively octavely related oscillations designatable as 4 foot, 8 foot, 16 foot etc., separate tone color circuits for each keyboard associated with said headers, a plurality of decoupling impedances respectively connected in series with said headers, a plurality of thermionic tubes each having an anode, a control grid and a cathode, the output end of said impedances being respectively connected to grids of said tubes, the cathodes of said tubes being connected to a common return path, the plates of said tubes being respectively connected to at least one of said tone color circuits and coupling circuits respectively connected between input ends of decoupling impedances in series with the headers of one keyboard and output ends of decoupling impedances in series with headers of divergent designations of another keyboard.

12. The combination claimed in claim 11 wherein each coupling circuit comprises a switch and a first impedance in series, said switch being adjacent said input end and said first impedance being adjacent said output end, and a second impedance connected between the junction of said switch with said first impedance and a common return path.

13. In an electrical musical instrument, a plurality of headers for collecting respectively octavely related oscillations designatable as 4-foot. 8-foot, 16-foot, etc., separate tone color circuits associated with such headers and similarly designatable, a decoupling impedance located in series in each such header, and coupler circuits each connecting the input end of an impedance in series in a header with the output end of an impedance in series in another header.

RAYMOND P. MORK.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,233,948 Kock Mar. 4, 1941 2,403,664 Langer July 9, 1946 

